Systems for sensing tire conditions and displaying sensed tire condition information to a vehicle occupant are known. Often, such systems are known as tire pressure monitoring (“TPM”) systems even though the system may sense tire conditions in addition to pressure, such as tire temperature. Such TPM systems include a tire-based sensor assembly that senses, for example, the air pressure and temperature inside its associated tire and transmits the sensed tire condition information to a vehicle-based receiver, i.e., a receiver mounted in the vehicle. The transmitted sensed tire condition signal may be a coded radio frequency (“RF”) signal. The vehicle-based receiver is connected to a display located in the vehicle cabin so as to display, for example, a warning signal to the vehicle operator when an under-inflated tire pressure condition exists or an over-heated tire condition occurs.
Each tire-based sensor assembly may have a unique identification (“ID”) code associate therewith. The tire-based sensor assembly may transmit a signal that includes its associated unique ID code along with the sensed tire condition. The vehicle-based receiver can associate the received tire signal and unique ID with a particular tire location on the vehicle such as front right (“FR”), front left (“FL”), rear right (“RR”), or rear left (“RL”). By associating the tire ID with the tire location on the vehicle, the vehicle-based receiver is able to display the sensed tire condition information at each particular tire location so the vehicle operator can identify which tire (i.e., tire location) has a sensed, improper condition.
Associating a tire location with a tire-based transmitted ID code for each of the tire locations requires a “learning” process by the vehicle-based receiver. Methods have been proposed to accomplish this learning process. The simplest learning system includes preprogramming the vehicle-based receiver with the ID's of each of the tire-based sensors along with their present location. When the tires are rotated or a sensor is replaced, the vehicle-based system must be reprogrammed. Other arrangements have been proposed that automate the learning process. One such system uses localized signal interrogation in which each tire-based sensor assembly includes a receiver that is separately interrogated from a transmitter located outside of the tire using, for example, a localized low frequency (“LF”) interrogation signal controlled by the vehicle-based receiver. In response to receiving an interrogation signal, the tire-based sensor assembly transmits a response signal having its unique ID. Upon receipt of the response signal, the vehicle-based receiver associates that unique tire ID with that tire location since the system “knows” which tire location was just interrogated. The vehicle-based system stores tire-based sensor IDs and tire location associations in memory for later use in its display operation. The interrogation process could occur at each vehicle start-up to automatically account for tire rotation and/or sensor replacement.
Some TPM systems have been proposed in which the tire-based system includes a tire rotation sensor that measures wheel rpm's (revolutions per minute). The tire-based system transmits a tire ID, tire rotation rpm values, and tire condition information. Each tire has an associated external wheel rotation sensor that also monitors wheel rpm's. A vehicle-based receiver receives and compares the two rpm values and associates the tire ID with location of the tire in response to matching the rpm values.
U.S. Patent Application 2012/0112899A1 to Hannon and assigned to the same assignee of the present invention discloses a method and apparatus for determining tire condition and location using a tire-based sensor having a unique ID, a tire condition sensor, and further includes an acceleration sensor for sensing when the tire rotates through one of two positions. A wheel speed sensor is connected to a vehicle-based receiver. The vehicle-based receiver associates tire ID with tire location in response to the reception of the tire condition signal and in response to the wheel speed sensor signal.